package org.frameworkset.schedule;
import java.util.LinkedList;
import java.util.Queue;
import org.frameworkset.util.Assert;
public class ListenableFutureCallbackRegistry<T> {
private final Queue<ListenableFutureCallback<? super T>> callbacks =
new LinkedList<ListenableFutureCallback<? super T>>();
private State state = State.NEW;
private Object result = null;
private final Object mutex = new Object();
/**
* Adds the given callback to this registry.
* @param callback the callback to add
*/
@SuppressWarnings("unchecked")
public void addCallback(ListenableFutureCallback<? super T> callback) {
Assert.notNull(callback, "'callback' must not be null");
synchronized (mutex) {
switch (state) {
case NEW:
callbacks.add(callback);
break;
case SUCCESS:
callback.onSuccess((T)result);
break;
case FAILURE:
callback.onFailure((Throwable) result);
break;
}
}
}
/**
* Triggers a {@link ListenableFutureCallback#onSuccess(Object)} call on all added
* callbacks with the given result
* @param result the result to trigger the callbacks with
*/
public void success(T result) {
synchronized (mutex) {
state = State.SUCCESS;
this.result = result;
while (!callbacks.isEmpty()) {
callbacks.poll().onSuccess(result);
}
}
}
/**
* Triggers a {@link ListenableFutureCallback#onFailure(Throwable)} call on all added
* callbacks with the given {@code Throwable}.
* @param t the exception to trigger the callbacks with
*/
public void failure(Throwable t) {
synchronized (mutex) {
state = State.FAILURE;
this.result = t;
while (!callbacks.isEmpty()) {
callbacks.poll().onFailure(t);
}
}
}
private enum State {NEW, SUCCESS, FAILURE}
}